Phenoloxidase activity and thermostability of Cancer pagurus and Limulus polyphemus hemocyanin.

The intrinsic and inducible o-diphenoloxidase (o-diPO) activity of Cancer pagurus hemocyanin (CpH) and Limulus polyphemus hemocyanin (LpH) were studied using catechol, l-Dopa and dopamine as substrates. The kinetic analysis shows that dopamine is a more specific substrate for CpH than catechol and l-Dopa (K(m) value of 0.01 mM for dopamine versus 0.

Reversible heat inactivation of copper sites precedes thermal unfolding of molluscan (Rapana thomasiana) hemocyanin.

Hemocyanin (Hc) is a type-3 copper protein, containing dioxygen-binding active sites consisting of paired copper atoms. In the present study the thermal unfolding of the Hc from the marine mollusc Rapana thomasiana (RtH) has been investigated by combining differential scanning calorimetry, Fourier transform infrared (FTIR) and UV-vis absorption spectroscopy. Two important stages in the unfolding pathway of the Hc molecule were discerned.

FTIR 2D correlation spectroscopy of α₁ and α₂ fractions of an alkali-pretreated gelatin.

An alkali-pretreated gelatin (pI~4.9) was fractionated by means of alcohol coacervation and semi-preparative gel chromatography. The thermal responses of the isolated α fractions, the coacervate and the total gelatin were investigated by 2D-correlation FTIR spectroscopy in the amide I band region (1600-1700 cm⁻¹).

Influence of limited proteolysis, detergent treatment and lyophilization on the phenoloxidase activity of Rapana thomasiana hemocyanin.

The intrinsic and inducible phenoloxidase (PO) activity of Rapana thomasiana hemocyanin (RtH) and its substructures were studied. With catechol as substrate, a weak o-diPO activity was measured for the didecameric RtH and its subunits. Some activation of the o-diPO activity of RtH was achieved by limited treatment with subtilisin and by incubation of RtH with 2.

Involvement of glycans in the immunological cross-reaction between alpha-macroglobulin and hemocyanin of the gastropod Helix pomatia.

By tandem-crossed immunoelectrophoresis and ELISA experiments an immunological relationship was observed between alpha-macroglobulin (alphaM) and hemocyanin (Hc) of the terrestrial snail Helix pomatia. Both glycoproteins occur in the hemolymph: alphaM (minor component) as a specific proteinase inhibitor, Hc (consisting of three components: alpha(D)-HpH, alpha(N)-HpH and beta-HpH) as oxygen transport protein. The cross-reaction was found to be correlated with glycosylation.